Electron Transfer Kinetics in a Triad Photo-anode for Light-driven Water-splitting Open Access

Han, Nannan (2013)

Permanent URL: https://etd.library.emory.edu/concern/etds/qb98mf937?locale=en
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Abstract

Efficient water oxidation remains a key challenge for the production of fuel from water. In this report, triadic water oxidizing photoanode has been assembled from nanoporous TiO2, a novel crown-ether derivative sensitizer [Ru(5-crownphen)2(dpb)]2+ (C2P2) and a polyoxometalate water oxidation catalyst [{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2]10- (POM). Visible and IR transient absorption measurements were used to monitor and compare the population change of C2P2 and electron injection into TiO2 in different systems of the C2P2 aqueous solution, C2P2/TiO2 and POM/C2P2/TiO2 respectively. Electron transfers from catalyst POM to sensitizer C2P2 were confirmed indicated the photogenerated oxidized C2P2 could effectively oxidize POM to generate the charge separate state (TiO2--C2P2-POM+) - the first of the four catalyst oxidation events needed for water oxidation. More work unraveling the parameters effects of the system such as pH dependence, power dependence, loading dependence etc. were studied.

Table of Contents

Abstract...iv

List of Abbreviations...viii

List of Figures...ix

List of Schemes...x

Chapter 1 Introduction... 1

1.1 General Introduction...2

1.2 Solar Energy Conversion Overview...4

1.3 Sunlight-Drive Water Splitting...8

1.4 Pump-Probe Transient Absorption Measurement...9

1.5 Summary of the Projects in the Thesis...9

References...11

Chapter 2 Experimental Methods and Preparation of Samples... 14

2.1 Preparation of the Water-Splitting Photoanodes...15

2.2 The Covalent POM-Photosensitizer Dyads Samples...17

2.3 Pump-probe Transient Absorption Spectroscopy...18

References... 21

Chapter 3 The Study of Electron Transfer Process in Water oxidizing POM/C2P2/TiO2 Triad Photoanodes...22

3.1 Transient Absorption Spectra of the C2P2/TiO2 (Dyad)...23

3.2 Transient Absorption Spectra of the POM/C2P2/TiO2 (Triad)...28

3.3 Parameters affecting ET from the catalyst POM to C2P2...30

3.4 Summary...33

References... 35

Chapter 4 Study the Electron Transfer of Organometallic-Redox Assemblies...36

4.1 Transient Absorption Spectra and Kinetics...37

4.2 Global Fitting Derivations...41

References...42

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